Electrochromic device including lithium-rich anti-perovskite material

ABSTRACT

An electrochromic device includes a light transmissive first substrate, a working electrode disposed on the first substrate, a light transmissive second substrate facing the first substrate, a counter electrode disposed on the second substrate, and a lithium-rich anti-perovskite (LiRAP) material disposed between the first and second substrates. The LiRAP material includes an ionically conductive and electrically insulating LiRAP material.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/007,488, filed on Jun. 13, 2018, which claims the benefit of priorityto U.S. Provisional Application Ser. No. 62/520,077, filed Jun. 15,2017, the entire content of the foregoing applications are incorporatedherein by reference.

FIELD

The present invention is generally directed to electrochromic (EC)devices including a lithium-rich anti-perovskite (LiRAP) materialconfigured to provide improved electrochemical stability and/or cyclelife.

BACKGROUND OF THE INVENTION

Currently, static window coatings can be manufactured at relatively lowcost. However, these window coatings are static and not well suited forlocations with varying climates. An electrochromic (EC) window coatingovercomes these limitations by enhancing the window performance in allclimates. EC window coatings undergo a reversible change in opticalproperties when driven by an applied potential. However, performance ofEC materials may degrade from use over time as a result of repeatedexposure to radiation in the ultraviolet (UV) light and/or reactionsbetween the electrolyte and electrodes of an EC device.

SUMMARY OF THE INVENTION

According to various embodiments, provided is an EC device including alight transmissive first substrate, a working electrode disposed on thefirst substrate, a light transmissive second substrate facing the firstsubstrate, a counter electrode disposed on the second substrate, and alithium-rich anti-perovskite (LiRAP) material disposed between the firstand second substrates. The LiRAP material includes an ionicallyconductive and electrically insulating LiRAP material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 are schematic representations of EC devices, according tovarious embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing disposed “on” or “connected to” another element or layer, it canbe directly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being disposed “directly on” or “directlyconnected to” another element or layer, there are no interveningelements or layers present. It will be understood that for the purposesof this disclosure, “at least one of X, Y, and Z” can be construed as Xonly, Y only, Z only, or any combination of two or more items X, Y, andZ (e.g., XYZ, XYY, YZ, ZZ).

While not intending to be bound to a particular theory, it is believedthat under prolonged exposure to UV (or higher energy) radiation, anelectrochromic (EC) device may undergo a visible darkening(photo-chromic darkening) that mimics the EC darkening of the EC device.In particular, the darkening may result from a photochromic effect intransition metal oxide bronze working electrodes, such as doped orundoped tungsten oxide (e.g. WO_(3-x) where 0≤x≤0.33), which limits theoptical dynamic range of the EC device.

EC devices may also experience charge transfer fade during long-term ECcycling. It is believed that the charge transfer fade may result fromside reactions between EC materials, such as nickel oxide counterelectrode materials, and organic electrolyte constituents. Chargetransfer fade may be compensated for by increasing the operationalvoltage range of an EC device. However, higher operational voltages mayresult in and/or increase the generation of gas bubbles at one or moreelectrodes of an EC device. Such gas bubbles may decreaseelectrolyte-electrode contact and/or reduce EC device cycle life.

LiRAP Materials

In view of the above and/or other problems, various embodiments provideEC devices that include a Li-rich anti-perovskite (LiRAP) material. Anantiperovskite is a compound having a crystal structure like aconventional perovskite but with the unit cell having the positive andnegative species reversed. In a perovskite structure, the unit cell isface centered cubic. The negative atoms normally sit on the face centersand positive ions sit in the corners. Additionally, there will be athird type of atom, a cation, in the center of the cubic unit cell. Inan antiperovskite structure, the locations of cations and anions arereversed. In the antiperovskite structure, of the type described herein,oxygen or sulfur atoms, for example, reside at centers of the unit cell,halogen atoms sit at corners of the unit cell, and lithium ions residein the face centers of the unit cell. It is believed that the facecentered species may be the most mobile species in the unit cell.

The LiRAP material may be ionically conductive and electricallyinsulating. The LiRAP material may be included as a layer, coating,and/or matrix in an EC device and may operate to improve cycle lifetimeand/or durability of the EC device. In some embodiments, the LiRAPmaterial may be configured to reduce the energy difference between thevalence band of metal oxide nanostructured EC material (e.g., tungstenoxide) and the oxidation potential of adjacent molecules (e.g.,molecules of adjacent organic electrolyte). This reduction then reducesthe driving force for electron-hole separation, promotes recombination,and reduces UV-induced photochromic darkening.

In other embodiments, the LiRAP material may be configured to reduce thegeneration of gas bubbles in the organic electrolyte of an EC device.The LiRAP material may be configured to aid in the retention ofelectrode charge, by stabilizing the oxidation state of an electrode.For example, a nickel oxide counter electrode may be “charged” byoxidizing Ni²⁺ in the counter electrode to form Ni³⁺, via ozonation, andthe LiRAP material may be configured to prevent or reduce the reductionof Ni³⁺ to Ni²⁺.

According to various embodiments, EC devices may include one or morelayers of the LiRAP material. The LiRAP layer may be disposed on one ormore electrodes of an EC device. For example, a LiRAP layer may bedisposed between the counter electrode and the electrolyte of an ECdevice and/or between the working electrode and the electrolyte of an ECdevice. In other embodiments, the LiRAP material may be incorporatedinto a working electrode of an EC device. For example, the LiRAPmaterial may form a core-shell structure with the working electrodematerial, with particles of the working electrode being encapsulated bythe LiRAP material. In other embodiments, the LiRAP material may form amatrix around particles of the working electrode material.

In some embodiments, the LiRAP material may be used as an electrolytelayer in place of a conventional electrolyte, in an EC device. As such,the generation of gas by organic constituents of conventional organicmaterials may be prevented. A LiRAP electrolyte layer may also operateto widen the operating voltage range of an EC device, thereby improvingthe dark state light-blocking properties of an EC device and/or reducingthe transition time between light and dark states of an EC device.

According to various embodiments, the LiRAP material may the formulaLi₃OX, where X may be a halogen or a combination of halogens. Forexample, X may be F, Cl, Br, I, or any combination thereof. In someembodiments, the LiRAP material may be Li₃OI. In some embodiments, theLiRAP material may also include one or more dopant species. In someembodiments, the LiRAP material may be aliovalently doped by replacing afirst anion in the base structure with a second anion that has a valencemore positive than that of the first atom.

The LiRAP material may be formed from constituent lithium salts. Forexample, the LiRAP material may be formed from an oxygen-containinglithium salt and a halogen salt of lithium. Examples of theoxygen-containing lithium salt include lithium hydroxide (LiOH) lithiumacetate (C₂H₃LiO₂), lithium carbonate (Li₂CO₃), lithium oxide (Li₂O),lithium perchlorate (LiClO₄), lithium nitrate (LiNO₃), or anycombination thereof. Examples of the halogen salt of lithium includelithium chloride (LiCl), lithium bromide (LiBr), lithium fluoride (LiF),lithium iodide (LiI), or any combination thereof. In some embodiments,the LiRAP material may be formed from LiOH and LiI.

The LiRAP material may be formed by solution deposition or any othersuitable method. In particular, when a layer of LiRAP material is formedby solution deposition, a solution containing the precursor salts may beformed. The solution may include an oxygen-containing lithium salt(e.g., LiOH or LiNO₃), at a concentration of about 1M (i.e., 1mole/liter). Depending on the application, the oxygen-containing lithiumsalt can be at concentration ranging from about 0.01M to about 2M. Thesolution may also contain a halogen salt of lithium (e.g., LiI), at aconcentration of about 0.5M, for example, but it is to be appreciatedthat other concentration or amounts are possible as well. The ratiobetween oxygen-containing lithium salt and the hydrogen salt of lithiumcan be around 2:1, which is chosen based on empirical data to maximizeionic conductivity. Stoichiometrically, ratios of 2:1, 1:1, and 4:3represent useful oxygen-containing lithium salt to the hydrogen salt oflithium ratios to achieve desired materials.

The solution may also contain a solvent or co-solvents. For example,water, methanol, and ethanol represent some of the solvents in whichLiOH is soluble. For other lithium salts, butanol, dimethyl sulfoxide(DMSO), and/or dimethylformamide (DMF) can be used as a solvent. Thetype of solvent system is limited by the precursor with lowestsolubility. In various embodiments, methanol and water are used asco-solvents.

Once prepared, the solution may be applied to a substrate. The solutionmay be coated on the substrate using, for example, a doctor blade orother suitable coating method. In some embodiments, the substrate may bea component of an EC device, such as a working electrode or a counterelectrode. The deposited substrate may then be dried.

The dried substrate may then be thermally annealed at a temperatureranging from about 180° C. to 400° C., for a time period ranging fromabout 45 minutes to 3 days, to form a LiRAP layer/composition. In someembodiments, the dried substrate may be annealed at a temperature ofabout 330° C., for about 180 minutes, to form a LiRAP layer. Thesubstrate may then be assembled with other components, to form an ECdevice.

EC Devices

FIGS. 1-5 are schematic views of EC devices, according to variousembodiments of the present disclosure. It should be noted that such ECdevices may be oriented upside down or sideways from the orientationsillustrated in FIGS. 1-5. Furthermore, the thickness of the layersand/or size of the components of the devices in FIGS. 1-5 are not drawnto scale or in actual proportion to one another other, but rather areshown as representations.

Referring to FIG. 1, an exemplary EC device 100 may include opposingfirst and second substrates 102, 104. The first and second substrates102, 104 may transparent substrates, such as substrates formed of glassor plastic. However, in some embodiments, the substrates 102, 104 may beomitted.

First and second transparent conductors 106, 108 may be respectivelydisposed on the first and second substrates 102, 104. A counterelectrode 112 may be disposed on the first transparent conductor 106,and a working electrode 110 may be disposed on the second transparentconductor 108. A solid state electrolyte 114 may be disposed on theworking electrode 110, and a LiRAP layer 120 may be disposed on thecounter electrode 112.

The first and second transparent conductors 106, 108 may be formed fromtransparent conducting films fabricated using inorganic and/or organicmaterials. For example, the transparent conductors 106, 108 may includeinorganic films of transparent conducting oxide (TCO) materials, such asindium tin oxide (ITO) or fluorine doped tin oxide (FTO). In otherexamples, organic films of transparent conductors 106, 108 may includegraphene and/or various polymers.

The counter electrode 112 should be capable of storing enough charge tosufficiently balance the charge needed to cause visible tinting to thenanostructured transition metal oxide nanostructures in the workingelectrode 110. In various embodiments, the counter electrode 112 may beformed as a conventional, single component film, a nanostructured film,or a nanocomposite layer.

In some embodiments, the counter electrode 112 may be formed from atleast one passive material that is optically transparent to both visibleand NIR radiation during the applied biases. Examples of such passivecounter electrode materials may include CeO₂, CeVO₂, TiO₂, indium tinoxide, indium oxide, tin oxide, manganese or antimony doped tin oxide,aluminum doped zinc oxide, zinc oxide, gallium zinc oxide, indiumgallium zinc oxide, molybdenum doped indium oxide, Fe₂O₃, V₂O₅, ormixtures thereof. In other embodiments the counter electrode 112 may beformed from at least one complementary material, which may betransparent to NIR radiation but which may be oxidized in response toapplication of a bias, thereby causing absorption of visible lightradiation. Examples of such complementary counter electrode materialsmay include Cr₂O₃, MnO₂, FeO₂, CoO₂, nickel oxide (e.g., NiO_(x), where1≤x≤1.5, such as NiO), RhO₂, or IrO₂. The counter electrode materialsmay include a mixture of one or more passive materials and/or one ormore complementary materials described above.

The LiRAP layer 120 may have a thickness of less than about 2 μm, suchas a thickness of 300 nm or less, or a thickness ranging from about 2 to200 nm.

The LiRAP layer 120 may be configured to stabilize the oxidation stateof the counter electrode 112, which may aid in the retention of anelectrical charge applied to the counter electrode 112. For example,when the counter electrode 112 includes NiO, the counter electrode 112may be “charged” via ozonation, which may operate to convert the Ni²⁺ toNi³⁺. The LiRAP layer 120 may be configured to prevent electricalinteractions between the counter electrode 112 and the electrolyte 114,thereby reducing and/or preventing such interactions from reducing theNi³⁺ back to Ni²⁺ in the nickel oxide, as would readily occur in theabsence of the LiRAP layer 120. The LiRAP layer 120 may also preventand/or reduce the generation of gas bubbles in the electrolyte 114 atthe counter electrode 112, which may be due to side reactions betweencomponents of the electrolyte 114 and the counter electrode 112, duringoperation of the EC device 100.

In the various embodiments, the working electrode 110 may include dopedor undoped transition metal oxide nanostructures 110A, and optionallytransparent conducting oxide (TCO) nanostructures 110B, which are shownschematically as circles and hexagons for illustration purposes only. Asdiscussed above, the thickness of the layers of the device 100,including and the shape, size and scale of nanostructures is not drawnto scale or in actual proportion to each other, but is represented forclarity. In the various embodiments, nanostructures 110A, 110B may beembedded in an optically transparent matrix material or provided as apacked or loose layer of nanostructures exposed to the electrolyte.

In the various embodiments, the doped transition metal oxidenanostructures 110A may be a ternary composition of the type AxMzOy,where M represents a transition metal ion species in at least onetransition metal oxide, and A represents at least one dopant. Transitionmetal oxides that may be used in the various embodiments include, butare not limited to any transition metal oxide which can be reduced andhas multiple oxidation states, such as niobium oxide, tungsten oxide,molybdenum oxide, vanadium oxide, titanium oxide and mixtures of two ormore thereof. In one example, the transition metal oxide nanostructuresmay include doped or undoped tungsten oxide (WO_(3-x)) nanoparticles,where 0≤x≤0.33, such as 0≤x≤0.1.

In various embodiments, the at least one dopant species may be a firstdopant species that, upon application of a particular first voltagerange, causes a first optical response. The applied voltage may be, forexample, a negative bias voltage. Specifically, the first dopant speciesmay cause a surface plasmon resonance effect on the transition metaloxide by creating a significant population of delocalized electroniccarriers. Such surface plasmon resonance may cause absorption of NIRradiation at wavelengths of around 780-2000 nm, with a peak absorbanceat around 1200 nm. In various embodiments, the specific absorbances atdifferent wavelengths may be varied/adjusted based other factors (e.g.,nanostructure shape, size, etc.), discussed in further detail below. Inthe various embodiments, the first dopant species may be an ion speciesselected from the group of cesium, rubidium, and lanthanides (e.g.,cerium, lanthanum, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, and lutetium).

In various embodiments, the dopant may include a second dopant speciesthat causes a second optical response based upon application of avoltage within a different, second particular range. The applied voltagemay be, for example, a negative bias voltage. In an embodiment, thesecond dopant species may migrate between the solid state electrolyte114 and the transition metal oxide nanostructures of the workingelectrode 110, as a result of the applied voltage. Specifically, theapplication of voltage within the particular range may cause the seconddopant species to intercalate and deintercalate the transition metaloxide nanostructures. In this manner, the second dopant may cause achange in the oxidation state of the transition metal oxide, which maycause a polaron effect and a shift in the lattice structure of thetransition metal oxide. This shift may cause absorption of visibleradiation, for example, at wavelengths of around 400-780 nm.

In various embodiments, the second dopant species may be anintercalation ion species selected from the group of lanthanides (e.g.,cerium, lanthanum, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, and lutetium), alkali metals (e.g., lithium, sodium,potassium, rubidium, and cesium), and alkali earth metals (e.g.,beryllium, magnesium, calcium, strontium, and barium). In otherembodiments, the second dopant species may include a charged protonspecies. For example, if the transition metal oxide nanostructures 110Aare WO_(3-X) nanoparticles, the dopant may be Li intercalated from theelectrolyte 114.

In various embodiments, the TCO nanostructures 110B may optionally bemixed with the transition metal oxide nanostructures 110A in the workingelectrode 110. In the various embodiments, the TCO nanostructures 110Bmay include at least one TCO composition, which prevents UV radiationfrom reaching the electrolyte and generating electrons. In an exampleembodiment, the nanostructures 110B may include an indium tin oxide(ITO) composition, which may be a solid solution of around 60-95 wt %(e.g., 85-90 wt %) indium(III) oxide (In₂O₃) and around 5-40 wt % (e.g.,10-15 wt %) tin(IV) oxide (SnO₂). In another example embodiment, the TCOnanostructures 110B may include an aluminum-doped zinc oxide (AZO)composition, which may be a solid solution of around 99 wt % zinc oxide(ZnO) and around 2 wt % aluminum(III) oxide (Al₂O₃). Additional oralternative TCO compositions that may be used to form nanostructures110B in the various embodiments include, but are not limited to, indiumoxide, zinc oxide and other doped zinc oxides such as gallium-doped zincoxide and indium-doped zinc oxide.

The TCO material of the nanostructures 110B may be transparent tovisible light and, upon application of the first voltage, may modulateabsorption of NIR radiation at wavelengths of around 1200-2500 nm, withpeak absorbance around 2000 nm (e.g., at a longer peak wavelength thanthe transition metal oxide nanostructures 110A, but with overlappingabsorption bands). In particular, application of the first voltage maycause an increase in free electron charge carriers, and therefore causea surface plasmon resonance effect in at least one TCO nanostructures110B. In an embodiment in which the TCO composition is ITO, the surfaceplasmon resonance effect may be caused by oscillation of free electronsproduced by the replacement of indium ions (In³⁺) with tin ions (Sn⁴⁺).Similar to the transition metal oxide bronze, such surface plasmonresonance may cause a change in absorption properties of the TCOmaterial. In some embodiments, the change in absorption properties maybe an increase in absorbance of NIR radiation at wavelengths thatoverlaps with that of the nanostructures 110A. Therefore, the additionof TCO nanostructures 110B to the working electrode 110 may serve toexpand the range of NIR radiation absorbed (e.g., at wavelengths ofaround 780-2500 nm) compared to that of the nanostructures 110A alone(e.g., at wavelengths of around 780-2000 nm), and to enhance absorptionof some of that NIR radiation (e.g., at wavelengths of around 1200-2000nm).

Based on these optical effects, the nanostructures 110A and optionalnanostructures 110B of the working electrode 110 may progressivelymodulate transmittance of NIR and visible radiation as a function ofapplied voltage by operating in at least three different modes. Forexample, a first mode may be a highly solar transparent (“bright”) modein which the working electrode 110 is transparent to NIR radiation andvisible light radiation. A second mode may be a selective-IR blocking(“cool”) mode in which the working electrode 110 is transparent tovisible light radiation but absorbs NIR radiation. A third mode may be avisible blocking (“dark”) mode in which the working electrode 110absorbs radiation in the visible spectral region and at least a portionof the NIR spectral region. In an example, application of a firstvoltage having a negative bias may cause the EC device to operate in thecool mode, blocking transmittance of NIR radiation at wavelengths ofaround 780-2500 nm. In another example, application of a second negativebias voltage having a higher absolute value than the first voltage maycause the EC device to operate in the dark state, blocking transmittanceof visible radiation (e.g., at wavelengths of around 400-780 nm) and NIRradiation at wavelengths of around 780-1200 nm. In another example,application of a third voltage having a positive bias may cause the ECdevice to operate in the bright state, allowing transmittance ofradiation in both the visible and NIR spectral regions. In variousembodiments, the applied voltage may be between −5V and 5V, preferablybetween −2V and 2V. For example, the first voltage may be −0.25V to−0.75V, and the second voltage may be −1V to −2V. In another example,the absorbance of radiation at a wavelength of 800-1500 nm by the ECdevice may be at least 50% greater than its absorbance of radiation at awavelength of 450-600 nm.

Alternatively, the nanostructures 110A and optional nanostructures 110Bof the working electrode 110 may modulate transmittance of NIR andvisible radiation as a function of applied voltage by operating in twodifferent modes. For example, a first mode may be a highly solartransparent (“bright”) mode in which the working electrode 110 istransparent to NIR radiation and visible light radiation. A second modemay be a visible blocking (“dark”) mode in which the working electrode110 absorbs radiation in the visible spectral region and at least aportion of the NIR spectral region. In an example, application of afirst voltage having a negative bias may cause the EC device to operatein the dark mode, blocking transmittance of visible and NIR radiation atwavelengths of around 780-2500 nm. In another example, application of asecond voltage having a positive bias may cause the EC device to operatein the bright mode, allowing transmittance of radiation in both thevisible and NIR spectral regions. In various embodiments, the appliedvoltage may be between −2V and 2V. For example, the first voltage may be−2V, and the second voltage may be 2V.

In various embodiments, the shape, size, and doping levels ofnanostructured transition metal oxide nanostructures may be tuned tofurther contribute to the spectral response by the device. For instance,the use of rod versus spherical nanostructures 110A may provide a widerlevel of porosity, which may enhance the switching kinetics. Further, adifferent range of dynamic plasmonic control may occur fornanostructures with multiple facets, such as at least 20 facets.

Various embodiments may also involve alternation of the nanostructures110A that form the working electrode 110. For example, thenanostructures may be nanoparticles of various shapes, sizes and/orother characteristics that may influence the absorption of NIR and/orvisible light radiation. In some embodiments, the nanostructures 110Amay be isohedrons that have multiple facets, preferably at least 20facets.

In some embodiments, the transition metal oxide nanostructures 110A maybe a combination of nanoparticles having a cubic unit cell crystallattice (“cubic nanoparticles”) and nanoparticles having a hexagonalunit cell crystal lattice (“hexagonal nanoparticles”). Each unit celltype nanoparticle contributes to the performance of the workingelectrode 110. For example, the working electrode 110 may include bothcubic and hexagonal cesium doped tungsten oxide bronze nanoparticles. Inalternative embodiments, the working electrode 110 may include eithercubic or hexagonal cesium doped tungsten oxide nanoparticles. Forexample, the working electrode 110 may include cubic cesium-dopedtungsten oxide (e.g. Cs₁W₂O_(6-X)) nanoparticles and amorphous niobiumoxide nanoparticles or hexagonal cesium-doped tungsten oxide (e.g.Cs_(0.29)W₁O₃) nanoparticles without niobium oxide. In alternativeembodiments, the working electrode 110 may include undoped cubictungsten oxide (e.g. WO_(3-X)) nanoparticles where 0≤X≤0.1.

In some embodiments, the working electrode and/or the counter electrodemay additionally include at least one material, such as an amorphousnanostructured material, that enhances spectral absorption in the lowerwavelength range of the visible region. In some embodiments, the atleast one amorphous nanostructured material may be at least onenanostructured amorphous transition metal oxide.

In particular, the amorphous nanostructured materials may provide colorbalancing to the visible light absorption that may occur due to thepolaron-type shift in the spectral absorption of the doped-transitionmetal oxide bronze. As discussed above, upon application of the secondvoltage having a higher absolute value, the transition metal oxidebronze may block (i.e., absorb) radiation in the visible range. Invarious embodiments, the absorbed visible radiation may have wavelengthsin the upper visible wavelength range (e.g., 500-700 nm), which maycause the darkened layer to appear blue/violet corresponding to theun-absorbed lower visible wavelength range (e.g., around 400-500 nm). Invarious embodiments, upon application of the second voltage, the atleast one nanostructured amorphous transition metal oxide may absorbcomplementary visible radiation in the lower visible wavelength range(e.g., 400-500 nm), thereby providing a more even and complete darkeningacross the visible spectrum with application of the second voltage. Thatis, use of the amorphous nanostructured material may cause the darkenedlayer to appear black.

In some embodiments, at least one nanostructured amorphous transitionmetal oxide may be included in the working electrode 110 in addition tothe doped-transition metal oxide nanostructures 110A and the optionalTCO nanostructures 110B. An example of such material in the workingelectrode 110 may be, but is not limited to, nanostructured amorphousniobium oxide, such as NbO, NbO₂, or Nb₂O₅. In some embodiments, thecounter electrode 112 may include, as a complementary material, at leastone nanostructured amorphous transition metal oxide. That is, inaddition to optically passive materials, the counter electrode 112 mayinclude at least one material for color balancing (i.e., complementing)the visible radiation absorbed in the working electrode (i.e., by thetransition metal oxide bronze. An example of such material in thecounter electrode 112 may be, but is not limited to, nanostructuredamorphous nickel oxide, such as nickel(II) oxide (NiO) or other nickeloxide materials (e.g., NiO_(x)).

In the various embodiments, nanostructures that form the working and/orcounter electrode, including the at least one amorphous nanostructuredmaterial, may be mixed together in a single layer. An example of a mixedlayer is shown in FIG. 1 with respect to transition metal oxidenanostructures 110A and TCO nanostructures 110B. Alternatively,nanostructures that form the working and/or counter electrode, includingthe at least one amorphous nanostructured material, may be separatelylayered according to composition. For example, a working electrode mayinclude a layer of amorphous NbO, nanostructures, a layer of transitionmetal oxide bronze nanostructures, and a layer of ITO nanostructures, inany of a number of orders.

In various embodiments, the electrolyte 114 may be a solid stateelectrolyte including a polymer material and a plasticizer material,such that electrolyte 114 may permeate into crevices between thetransition metal oxide nanostructures 110A (and/or nanostructures 110Bif present). The term “solid state,” as used herein with respect to theelectrolyte 114, refers to a polymer-gel and/or any other non-liquidmaterial. In some embodiments, the solid state electrolyte 114 mayfurther include a salt containing, for example, an ion species selectedfrom the group of lanthanides (e.g., cerium, lanthanum, praseodymium,neodymium, promethium, samarium, europium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium, and lutetium), alkalimetals (e.g., lithium, sodium, potassium, rubidium, and cesium), andalkali earth metals (e.g., beryllium, magnesium, calcium, strontium, andbarium). In an example embodiment, such salt in the electrolyte 114 maycontain a lithium and/or sodium ions. In some embodiments, the solidstate electrolyte 114 may initially contain a solvent, such as butanol,which may be evaporated off once the EC device 100 is assembled. In someembodiments, the electrolyte 114 may be around 40-60 wt % plasticizermaterial, preferably around 50-55 wt % plasticizer material. In anembodiment, the plasticizer material may include at least one oftetraglyme and an alkyl hydroperoxide. In an embodiment, the polymermaterial of the solid state electrolyte 114 may be polyvinylbutyral(PVB), and the salt may be lithium bis(trifluoromethane). In otherembodiments, the electrolyte 114 may include at least one of lithiumphosphorus oxynitride (LiPON) and tantalum pentoxide (Ta₂O₅).

In some embodiments, the electrolyte 114 may include a sacrificial redoxagent (SRA). Suitable classes of SRAs may include, but are not limitedto, alcohols, nitrogen heterocycles, alkenes, and functionalizedhydrobenzenes. Specific examples of suitable SRAs may include benzylalcohol, 4-methylbenzyl alcohol, 4-methoxybenzyl alcohol, dimethylbenzylalcohol (3,5-dimethylbenzyl alcohol, 2,4-dimethylbenzyl alcohol etc.),other substituted benzyl alcohols, indoline,1,2,3,4-tetrahydrocarbazole, N,N-dimethylaniline, 2,5-dihydroanisole,etc. In various embodiments, the SRA molecules may create an air stablelayer that does not require an inert environment to maintain charge.

Polymers that may be part of the electrolyte 114 may include, but arenot limited to, poly(methyl methacrylate) (PMMA), poly(vinylbutyral-co-vinyl alcohol-co-vinyl acetate) (PVB), poly(ethylene oxide)(PEO), fluorinated co-polymers such as poly(vinylidenefluoride-co-hexafluoropropylene), poly(acrylonitrile) (PAN), poly(vinylalcohol) (PVA), etc. Plasticizers that may be part of the polymerelectrolyte formulation include, but are not limited to, glymes(tetraglyme, triglyme, diglyme etc.), propylene carbonate, ethylenecarbonate, ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate,1-butyl-3-methylimidazolium hexafluorophosphate,1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide,1-butyl-1-methyl-pyrrolidinium bis(trifluoromethane sulfonyl)imide,etc.), N,N-dimethylacetamide, and mixtures thereof.

In some embodiments, the electrolyte 114 may include, by weight, 10-30%polymer, 40-80% plasticizer, 5-25% lithium salt, and 0-10% SRA.

FIG. 2 is a schematic view of an EC device 200, according to variousembodiments of the present disclosure. The EC device 200 is similar tothe EC device 100, so only the differences therebetween will bediscussed in detail.

Referring to FIG. 2, the EC device 200 includes a LiRAP layer 220disposed between the electrolyte 114 and the working electrode 110. TheLiRAP layer 220 may have a thickness as described above with respect tothe LiRAP layer 120 of FIG. 1.

The LiRAP layer 220 may be configured to physically separate the workingelectrode 110 from the electrolyte 114, such that the side reactionsbetween the working electrode 110 and the electrolyte may be suppressed.In other words, the LiRAP layer 220 may be disposed directly between theelectrolyte 114 and the working electrode 110.

Without being bound to any particular theory, it is believed that themigration of intercalation ions between the electrolyte 114 and theworking electrode 110 is responsible for at least some of the device'scapability to modulate spectral absorption. Therefore, in order tomaintain operability of the device, the LiRAP material used to form theLiRAP layer 220 should also be ionically conductive. That is, thematerial of the LiRAP layer 220 may operate to block free electrons inthe solid state electrolyte 114 from reducing the transition metal oxidenanostructures 110A of the working electrode 110, while allowing thediffusion of ions of an intercalation dopant species (e.g., Na, Li,etc.) between the electrolyte 114 and working electrode 110. In thismanner, degradation of the transition metal oxide nanostructures 110A isreduced or prevented by controlling the effect of the absorbed UVradiation in addition to or instead of instead of blocking itsabsorption.

Accordingly, the LiRAP layer 220 may be electrically insulating. Assuch, the LiRAP layer may be configured to prevent free electron chargecarriers from contacting the working electrode 110, such that the chargecarriers may be prevented from electrochemically reducing the transitionmetal oxide nanostructures 110A. Therefore, the LiRAP layer 220 mayprevent and/or reduce unwanted photo-chromic darkening of the workingelectrode 110. Further, the LiRAP layer 220 may be ionically conductiveto permit proper operating of the EC device 200.

FIG. 3 is a schematic view of an EC device 300, according to variousembodiments of the present disclosure. The EC device 300 is similar tothe EC devices 100, 200, so only the differences therebetween will bediscussed in detail.

Referring to FIG. 3, the EC device 300 includes the LiRAP layer 120disposed between the counter electrode 112 and the electrolyte 114. TheEC device 300 also includes the LiRAP layer 220 disposed between theworking electrode 110 and the electrolyte 114. Accordingly, both theworking electrode 110 and the counter electrode 112 are protected fromthe above-described side reactions with the electrolyte 114, such as gasbubble generation, charge reduction, and/or photo-chromic darkening.

FIG. 4 is a schematic view of an EC device 400, according to variousembodiments of the present disclosure. The EC device 400 is similar tothe EC device 100, so only the differences therebetween will bediscussed in detail.

Referring to FIG. 4, the EC device 400 includes a LiRAP material 420 inwhich the working electrode 110 is disposed. In one embodiment, theLiRAP material 420 may be in the form of a matrix layer that surroundsthe nanostructures 110A (and optionally 110B) of the working electrode110. In an alternative embodiment, the LiRAP material 420 may be mixedwith the working electrode 110 to form a composite working electrode. Inanother alternative embodiment, the LiRAP material 420 may surround thenanostructures 110A (and optionally 110B) in a core-shell configuration.In other words, the LiRAP material 420 may be in the form of shells thatsurround each of the nanostructures 110A (and optionally 110B). Theshells may be formed on nanoparticle core structures, and the resultingcore-shell nanoparticles may be introduced into an EC device. As such,the working electrode 110 may be protected from unwanted side reactionswith components of the electrolyte 114. In some embodiments, the LiRAPmaterial 420 and the working electrode 110 may be formed by depositing amixture, such as an ink, comprising the nanostructures 110A (andoptionally 110B) and LiRAP precursors, on the transparent conductor 108and then converting the LiRAP precursors to a LiRAP material afterdeposition. In other embodiments, the LiRAP material 420 and the workingelectrode 110 may be formed by depositing a mixture, such as an ink,comprising the nanostructures 110A (and optionally 110B) and a LiRAPmaterial (which is already formed from the LiRAP precursors in a priorstep) on the transparent conductor 108. In some embodiments, the LiRAPprecursors may include LiNO₃ and LiI.

The EC device may also optionally include a LiRAP layer 120 disposedbetween the electrolyte 114 and the counter electrode 112 or a LiRAPmaterial mixed with the counter electrode 112. The LiRAP layer 120 maybe formed by depositing a precursor mixture (e.g., precursor ink)comprising LiNO₃ and LiI on the counter electrode 112 and converting theprecursors to a LiRAP layer, or by depositing LiRAP precursors or aLiRAP material together with the counter electrode 112 material to forma composite LiRAP—counter electrode layer. In one embodiment, if thecounter electrode 112 material comprises nanostructures, then the LiRAPmaterial can form a matrix in which nanostructures of the counterelectrode are disposed, the LiRAP material and the nanostructures of thecounter electrode form a composite counter electrode, or the LiRAPmaterial forms shells around the nanostructures of the counterelectrode. Accordingly, the counter electrode 112 may be protected fromunwanted side reactions with components of the electrolyte 114.

FIG. 5 is a schematic view of an EC device 500, according to variousembodiments of the present disclosure. The EC device 500 is similar tothe EC device 400, so only the differences therebetween will bediscussed in detail.

Referring to FIG. 5, the EC device 500 includes a LiRAP layer 520disposed between the working electrode 110 and the counter electrode112. The LiRAP layer may operate as an electrolyte of the EC device 500.As such, the EC device 500 does not include a solid state polymerelectrolyte, as discussed above with regard to FIGS. 1-4. In otherwords, the LiRAP layer 520 is disposed directly between the workingelectrode 110 and the counter electrode 112. Accordingly, the LiRAPlayer 520 may be referred to as an LiRAP layer electrolyte. The LiRAPlayer 520 may have a thickness of about 20 μm or less, such as athickness ranging from about 20 μm to about 5 μm, from about 18 μm toabout 10 μm, or about 16 μm to about 12 μm.

In some embodiments, the LiRAP layer 520 may be disposed in contact witha surface of the working electrode 110 that faces the counter electrode112. In other embodiments, the LiRAP layer 520 may impregnate theworking electrode 110, such that the LiRAP layer 520 forms a matrixaround the nanostructures 110A and optionally 110B of the workingelectrode 110.

The LiRAP layer 520 may be free or substantially free of organiccompounds. As such, the LiRAP layer 520 may prevent or reduce thegeneration of gas bubbles at the working and/or counter electrodes 110,112. The LiRAP layer 520 may also prevent and/or suppress photochromicdarkening of the working electrode 110. Further, the LiRAP layer 520 mayimprove the operational voltage and/or reduce a transmissive statechange time period of the EC device.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andmodifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention. Thedescription was chosen in order to explain the principles of theinvention and its practical application. It is intended that the scopeof the invention be defined by the claims appended hereto, and theirequivalents.

The invention claimed is:
 1. An electrochromic (EC) device comprising: alight transmissive first substrate; a working electrode disposed on thefirst substrate; a light transmissive second substrate facing the firstsubstrate; a counter electrode disposed on the second substrate; a solidstate electrolyte including a polymer material disposed between thecounter electrode and the working electrode; and a lithium-richanti-perovskite (LiRAP) material disposed between the first and secondsubstrates, the LiRAP material comprising an ionically conductive andelectrically insulating LiRAP material.
 2. The EC device of claim 1,wherein the LiRAP material is represented by the formula Li₃OX, whereinX is F, Cl, Br, I, or any combination thereof.
 3. The EC device of claim1, wherein the LiRAP material comprises Li₃OI.
 4. The EC device of claim1, wherein the LiRAP material comprises a LiRAP layer disposed betweenthe electrolyte and the counter electrode.
 5. The EC device of claim 1,wherein the LiRAP material comprises a LiRAP layer disposed between theelectrolyte and the working electrode.
 6. The EC device of claim 1,wherein the LiRAP material comprises: a first LiRAP layer disposedbetween the electrolyte and the counter electrode; and a second LiRAPlayer disposed between the electrolyte and the working electrode.
 7. TheEC device of claim 1, wherein: the working electrode comprisestransition metal oxide nanostructures; and the LiRAP material forms amatrix in which nanostructures of the working electrode are disposed,the LiRAP material and the nanostructures of the working electrode forma composite working electrode, or the LiRAP material forms shells aroundthe nanostructures of the working electrode.
 8. The EC device of claim1, wherein the LiRAP material is configured to reduce or prevent sidereactions between the working electrode and the solid state electrolytedisposed between the counter electrode and the working electrode.
 9. TheEC device of claim 1, wherein the LiRAP material is configured to reduceor prevent generation of gas bubbles in the solid state electrolytedisposed between the counter electrode and the working electrode. 10.The EC device of claim 1, wherein the LiRAP material is configured toreduce or prevent ultraviolet photochromic darkening of the workingelectrode.
 11. The EC device of claim 1, wherein the LiRAP material isformed from a precursor mixture comprising LiNO₃ and LiI.
 12. A methodof making an electrochromic (EC) device, comprising: providing a lighttransmissive first substrate; providing a precursor mixture comprisingat least one lithium salt of a lithium-rich anti-perovskite (LiRAP)precursor material and transition metal oxide nanostructures in asolvent on the first substrate; annealing the precursor mixture to forma working electrode on the first substrate; providing a lighttransmissive second substrate; forming a counter electrode on the secondsubstrate; and forming a solid state electrolyte including a polymermaterial between the counter electrode and the working electrode. 13.The method of claim 12, wherein: the at least one lithium salt comprisesan oxygen-containing lithium salt and a halogen salt of lithium; and thetransition metal oxide nanostructures comprise tungsten oxidenanostructures.
 14. The method of claim 13, wherein the at least onelithium salt comprises LiNO₃ and LiI.